The invention relates generally to mounting brackets for establishing a preselected orientation between two relatively movable surfaces. More specifically, the invention concerns brackets for use with distributing frame connector blocks in telephone central offices.
As telephone central office switching systems equipment has evolved from electromechanical systems, such as step-by-step and crossbar, to space division electronic switching systems and time division digital switching systems, requirements have significantly increased for provision of ways and means for rewiring trunk and line circuits from the outside plant to newly added apparatus embodying the updated technologies within the central office facilities. Cabling activity at the main distributing frame of the central office also is caused by increasing capacity of a particular switching system by providing additional equipment of the existing types.
Naturally, the most economic approach to replacing old equipment with new in a telephone central office is to re-use existing physical space to the maximum possible and practical extent. This goal of reuse extends to the existing mounting space on main distributing frames. To this end, connector blocks were developed which could be temporarily mounted at the main distributing frame for providing cross-connect fields to the outside plant from newly added apparatus. Typically, such connector blocks were mounted adjacent to existing horizontal terminal strip sections of the distributing frame. Then, after the new central office equipment was cut-over into service, the existing horizontal terminal strips were removed, and the new connector blocks were mounted in their place at the main distributing frame.
Now, as urbanization expands, the need is fast approaching for the capability of converting more and more central office equipment to more modern apparatus. Most such central offices already have connector blocks mounted in the space where new blocks will be mounted, thereby necessitating the use of a technique known as "double blocking" in effecting any subsequent central office equipment upgrade. With double blocking, new connector blocks are temporarily mounted in front of existing blocks. Then, after cut-over, the existing connector blocks are removed, and the new blocks are mounted.
A problem with using double blocking for many types of connector blocks arises because the cross-connect fields of the existing blocks are normally oriented in a substantially vertical plane facing outwardly of the main distributing frame. This configuration has precluded use of double blocking, since temporarily mounting a new block directly in front of an existing block would prevent adequate access to the existing terminal fields by the telephone central office technician prior to cut-over of the new central office equipment.
The alternatives to double blocking are unacceptable in terms of service interruptions or labor expense. Without the capability of double blocking to avoid service interruptions, the new connector blocks would have to be physically mounted wherever free space is available--not necessarily adjacent to the existing main distributing frame. This in turn would lead to excessively long jumper cabling and unacceptably high labor costs in moving and remounting the new connector blocks after cut-over of new equipment.
Therefore, there is a need for a method and apparatus for facilitating double blocking for connector blocks having a front facing, vertically oriented terminal field.